The effective sealing of cracks and joints in asphalt and concrete streets and highways has, for years, been a requisite of effective maintenance. For initial construction, as in sealing the space above a joint filler placed between two blocks of or between an asphalt and a concrete layer, a "hot pour" sealer is desirable, i.e. one which is supplied in solid form but may be melted at a reasonable temperature and poured into the joint for solidification. A "hot pour" sealer is generally preferable to permit a high degree of bonding of the sealer to the asphalt or concrete surfaces of the joint, with a better penetration of irregularities or small depressions, in the surface to be bonded. Such a sealer is also desirable for filling cracks which have developed in concrete or asphalt pavement through traffic stresses, temperature changes and the like, to prevent widening of a crack, as by spalling, with the production of a larger crack, a pothole or the like.
The primary purposes of crack sealing are to prevent the entry of water into the substrate bases or subgrade soils, which would cause softening and loss of bearing power, swelling, frost heave or shrinking, mud pumping, and similar consequences. A desirable property of a sealer is to prevent entry of gravel, rock or other detritus which might restrain the normal narrowing of a joint upon expansion of the asphalt or concrete during warmer or hot weather.
Federal Specification SS-S-164 dated Feb. 12, 1952 for "Sealer, Hot-Poured Typed, for Joints in Concrete" superseded Federal Specification SS-F-336a dated May 19, 1947, and covered joint sealers for use in sealing joints in concrete pavements, bridges and other structures. It became evident that such hot pour joint sealers could also be used to seal cracks and such use became prevalent. Compositions, including rubber or both rubber and asphalt, have been sold for this purpose for many years. Thus a SEALZ hot poured joint sealer was advertised in 1945 by Dispersions Process, Inc. of New York, N.Y. but manufactured at Nagautuck, Conn. under the management of U.S. Rubber Co. The product is stated to have been accepted since 1938, to comply with Federal Specification SS-F-336a, and to contain a specially prepared rubber, natural and synthetic resins and expanded pigments.
W. R. Meadows, Inc. of Elgin, Ill., advertised in 1960 a "Sealtight" hot pour rubber asphalt joint sealer manufactured and sold by it and stated to meet Federal Specification SS-S-164. The sale and use thereof have continued to this date, including the sale thereof since 1962 as "Sealtight 164." This hot pour sealer for many years comprised paving grade asphalt in excess of 50%, a substantial amount of ground scrap rubber, a lesser amount of filler and a minor amount of process oil. In more recent years, the amount of ground scrap rubber has been reduced and an SBR rubber has been substituted for a substantial portion of the scrap rubber. Also more recently, a variation of "Sealtight 164", sold as "Sealtight Hi-Spec", comprised paving grade asphalt in excess of 50%, a substantial amount of filler and lesser amounts of SBR rubber and process oil. This composition exhibited an improvement over "Sealtight 164" in the bond and resiliency, as well as better low temperatures properties. Due to the presence of both process oil and SBR rubber, these compositions appear to be relevant to the present invention, although none have exhibited the properties of the compositions of this invention, as will be pointed out later.
A series of U.S. patents have been issued, e.g. U.S. Pat. Nos. 3,844,668; 3,891,585; 3,919,148; 3,939,100; 4,018,730; 4,021,393; 4,069,182; 4,085,078; 4,113,401; and 4,137,204; each disclosing pavement repair material formed by the reaction of paving grade asphalt and a non-oil resistant rubber, in some with addition of ingredients, such as a diluent to reduce viscosity, an asphalt rubber soap or an asphalt solvent. In all of the above, the asphalt and rubber are heated to temperatures which may be as high as 500.degree. F. specifically to form a gel. Particularly, U.S. Pat. No. 4,021,393 discloses a method and composition for surfacing and repairing broken pavements with an elastomeric material having improved flexing properties at freezing temperatures without any significant loss of viscosity at high application temperatures, this material comprising the reaction product between paving grade asphalt and non-oil resistant rubber to which 3 to 20 percent of a malthene has been admixed. A malthene is defined as the oily or soft constituent of bitumen which is soluble in petroleum spirits. Prior to this invention, the best low temperature properties of a joint sealer have been those of an expensive silicone rubber material.
In U.S. Pat. No. 4,278,469, it is stated that a binder composition for repairing and surfacing broken asphalt pavements may be made by blending a highly aromatic fluidized catalytic cracking (FCC) main column bottoms or equivalent, such as thermofor catalytic cracking (TCC) bottoms and an asphalt soluble elastomer, such as a polymer, with natural and synthetic rubbers being particularly desirable, in an amount of 1 to 20 percent of the total weight of the binder. Of the two specific examples provided, the first involves FCC main column bottoms and ethylene-vinyl acetate constituting 20% of the total weight. This binder is heated and spread over a fatigued asphalt pavement. The other example involves a heated asphalt residuum of high paraffinic content to which is added ground tire rubber and TCC syntower bottoms equivalent in hydrogen content to the FCC bottoms of the first example. The proportions by weight are 40/50/10 of asphalt to TCC syntowner bottoms to scrap rubber. A sample of FCC bottoms was tested to ascertain whether it could be substituted for the process oil used in the present invention and the specific proportions of the preferred embodiments were utilized, i.e. the proportions of Example 1 and Example 2 hereinafter set forth, as well as the preferred heating, mixing and other conditions. The resulting product was subjected to the same tests as the products of this invention. It was found that FCC bottoms failed to produce a suitable product. Thus, each product produced by using FCC bottoms failed the 300% expansion test at -20.degree. F., although passing the 100% expansion test for 3 cycles at -20.degree. F. In addition, each product produced using FCC bottoms was unsatisfactory through susceptibility to heat, having too high a flow value when heated to 140.degree. F. for five hours with the sample placed at a 75.degree. angle, in a standard ASTM test.
Among the objects of this invention are to provide a new and improved composition for crack and joint sealing purposes, particularly for concrete or asphalt pavements, highways and the like; to provide such a composition which has improved adhesion and particularly an improved adhesion and maintenance of this adhesion at low temperatures; to provide such a composition which produces less stress on the interface bond between the sealer and the concrete or asphalt, particularly during contraction at low temperatures; to provide such a composition which will tend to limit the entry of gravel, rock and similar detrius; to provide such a composition which may be transported as a solid and heated to a reasonable temperature for application; to provide such a composition which is a visibly homogenous composition and free of any settling components when heated to a safe temperature; to provide such a composition which, when melted, has a uniform pouring consistency and will completely fill joints or cracks without the inclusion of large air holes or discontinuities; to provide such a composition which, at -20.degree. F. or -29.degree. C., can be extended at least three cycles, for 100% of its original width without rupture, as well as at least one cycle for 300% of its original width without rupture; to provide a novel method of making such a composition reliably and effectively; and to provide such a method which is readily carried out.